As my thanks got bigger I went from carrying buckets from the kitchen to my tanks.As my tanks got bigger I used a 120 lt plastic barrel with a pump to pump the water into the tanks I have now made a hose that can fit my kitchen tap so I can fill the tanks straight from the tap after adjusting the temp my question is adding the dechlorinator to the new tank do I as the tank is filling up and do I for the water I am replacing or dose for the whole tank.